Techniques for detecting jammers in a received signal are described. A jammer detector includes a jammer filter for attenuating transmit signals leaked into the receive path, a pulse generator for converting the interference signals into discrete-level pulses, and a pulse processor for determining the presence of jammers in the discrete-level pulses. In an exemplary embodiment, the pulse processor is configured to further discriminate among close-in jammers that are close to the desired receive frequency, far-away jammers, and jammers arising from the transmit signals leaked into the receive path. In another exemplary embodiment, hysteresis is provided in the pulse generator to enable the generation of reliable pulses. Further aspects include configuring the jammer detector for operation in a plurality of frequency bands and/or according to a plurality of communications standards.
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19. An apparatus for detecting jammers in a received signal, the apparatus comprising:
means for generating pulses based on comparing the received signal to a reference level; and
means for detecting the presence of a jammer in response to a determination that a pulse frequency metric of said generated pulses exceeds a threshold.
23. A method for detecting jammers in a received signal, the method comprising:
generating a pulse generator output signal comprising a set of discrete-amplitude pulses based on comparing the received signal to a reference level;
computing a pulse frequency metric for the pulse generator output signal over a time window;
accumulating the pulse frequency metric over a plurality of time windows to generate a first accumulated metric; and
generating a first jammer detection signal in response to a determination that the first accumulated metric exceeds a first threshold.
38. A computer program product for detecting jammers in a received signal, the product comprising:
a non-transitory computer-readable medium having software code recorded thereon, comprising:
code for causing a computer to input a plurality of digital pulses, the digital pulses generated by comparing a received signal to a reference level;
code for causing a computer to compute a pulse frequency metric for the digital pulses over a time window;
code for causing a computer to accumulate the pulse frequency metric over a plurality of time windows to generate a first accumulated metric; and
code for causing a computer to generate a first jammer detection signal in response to a determination that the first accumulated metric exceeds a first threshold.
1. An apparatus for detecting jammers in a received signal, the apparatus comprising:
a pulse generator, an input signal to the pulse generator coupled to the received the pulse generator comprising at least one comparator for generating an output signal comprising a set of discrete-amplitude pulses based on comparing the input signal to a reference level; and
a pulse processor, an input signal to the pulse processor coupled to the output signal of the pulse generator, the pulse processor configured to compute a pulse frequency metric for the pulse generator output signal over a time window, accumulate the pulse frequency metric over a plurality of time windows to generate a first accumulated metric, and generate a first jammer detection signal in response to a determination that the first accumulated metric exceeds a first threshold.
2. The apparatus of
3. The apparatus of
4. The apparatus of
a notch filter, an input signal to the notch filter coupled to the received signal, an output signal of the notch filter coupled to the input signal to the pulse generator.
5. The apparatus of
6. The apparatus of
7. The apparatus of
a first comparator comparing the pulse generator input signal to a positive reference level;
a second comparator comparing the pulse generator input signal to a negative reference level; and
an S-R latch having an S-input coupled to the output signal of the first comparator, and an R-input coupled to the output signal of the second comparator, the output signal of the S-R latch coupled to the output signal of the pulse generator.
8. The apparatus of
a low-pass filter coupled to the output signal of the S-R latch; and an AND gate having a first input coupled to the output of the S-R latch, and
a second input coupled to the output of the low-pass filter, the output signal of the AND gate coupled to the output signal of the pulse generator.
9. The apparatus of
10. The apparatus of
11. The apparatus of
12. The apparatus of
13. The apparatus of
14. The apparatus of
15. The apparatus of
16. The apparatus of
17. The apparatus of
dividing each time window into a plurality of sub-windows;
determining the total number of pulses in each sub-window; and
accumulating the total number of pulses in each sub-window into the target number of pulses Np only if the total number of pulses in the sub-window exceeds a predetermined threshold Ts.
18. The apparatus of
20. The apparatus of
means for detecting the presence of a close-in jammer versus a far-away jammer based on said generated pulses.
21. The apparatus of
means for providing hysteresis to the comparing the received signal to a reference level.
22. The apparatus of
24. The method of
25. The method of
26. The method of
configuring at least one notch frequency based on an operating frequency band of the receiver; and
notch filtering the received signal before generating the pulse generator output signal with the at least one notch frequency.
27. The method of
comparing the pulse generator input signal to a positive reference level to generate a first comparator output signal;
comparing the pulse generator input signal to a negative reference level to generate a second comparator output signal;
latching the first comparator output signal with a latch when the first comparator output signal transitions; and
resetting the latch when the second comparator output signal transitions.
28. The method of
low-pass filtering the output signal of the latch; and
providing the output signal of the latch and the low-pass filtered output signal to an AND gate to generate the pulse generator output signal.
29. The method of
incrementing the first accumulated metric every time window the target number of pulses Np exceeds a predetermined threshold TNp1.
30. The method of
decrementing the first accumulated metric every time window the target number of pulses Np does not exceed TNp1.
31. The method of
generating a second jammer detection signal based on whether a second accumulated metric based on the target number of pulses exceeds a second threshold.
32. The method of
33. The method of
34. The method of
35. The method of
36. The method of
dividing each time window into a plurality of sub-windows; determining the total number of pulses in each sub-window; and
accumulating the total number of pulses in each sub-window into the target number of pulses Np only if the total number of pulses in the sub-window exceeds a predetermined threshold Ts.
37. The apparatus of
39. The computer program product of
40. The computer program product of
code for causing a computer to increment the first accumulated metric every time window the target number of pulses Np exceeds a predetermined threshold TNp1.
41. The computer program product of
code for causing a computer to decrement the first accumulated metric every time window the target number of pulses Np does not exceed TNp1.
42. The computer program product of
code for causing a computer to generate a second jammer detection signal based on whether a second accumulated metric based on the target number of pulses exceeds a second threshold.
43. The computer program product of
44. The computer program product of
45. The computer program product of
46. The computer program product of
47. The computer program product of
code for causing a computer to divide each time window into a plurality of sub-windows;
code for causing a computer to determine the total number of pulses in each sub-window; and
code for causing a computer to accumulate the total number of pulses in each sub-window into the target number of pulses Np only if the total number of pulses in the sub-window exceeds a predetermined threshold Ts.
48. The computer program product of
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1. Field
The present disclosure relates generally to communications devices, and more specifically, to techniques for detecting interference in communications receivers.
2. Background
In a communications system, a receiver receives a signal from a transmitter, typically in the presence of noise and interference, and attempts to recover the information sent by the transmitter. Examples of interference may include TX jammers arising from signal leakage from a transmit (TX) signal path co-located with the receiver, as well as jammers derived from other sources. Strong jammers may desensitize a receiver due to, e.g., the non-linear characteristics of the receiver which may mix the jammer signals into the desired signal.
To deal with strong jammers, a receiver may be designed to support both normal and high-linearity operating modes. In the high-linearity operating mode, the receiver may offer better linearity characteristics to minimize the distortion caused by the strong jammers, typically at the cost of greater power consumption. The receiver may be configured to switch from a normal operating mode to a high-linearity operating mode upon the detection of strong enough jammers. This feature demands the availability of jammer detectors that can reliably sense the presence of strong jammers in a received signal.
It would be desirable to provide jammer detectors that are low-cost, reliable, and easily configurable for operation in a plurality of frequency bands and/or according to a plurality of communications standards.
An aspect of the present disclosure provides an apparatus for detecting jammers in a received signal, the apparatus comprising: a pulse generator, an input signal to the pulse generator coupled to the received signal, the pulse generator comprising at least one comparator for generating an output signal based on comparing the input signal to a reference level; and a pulse processor, an input signal to the pulse processor coupled to the output signal of the pulse generator, the pulse processor configured to compute a pulse frequency metric for the pulse generator output signal over a time window, accumulate the pulse frequency metric over a plurality of time windows to generate a first accumulated metric, and generate a first jammer detection signal if the first accumulated metric exceeds a first threshold.
Another aspect of the present disclosure provides an apparatus for detecting jammers in a received signal, the apparatus comprising: means for generating pulses based on comparing the received signal to a reference level; and means for detecting the presence of a jammer based on said generated pulses.
Yet another aspect of the present disclosure provides a method for detecting jammers in a received signal, the method comprising: generating a pulse generator output signal based on comparing the received signal to a reference level; computing a pulse frequency metric for the pulse generator output signal over a time window; accumulating the pulse frequency metric over a plurality of time windows to generate a first accumulated metric; and generating a first jammer detection signal if the first accumulated metric exceeds a first threshold.
Yet another aspect of the present disclosure provides a computer program product for detecting jammers in a received signal, the product comprising: computer-readable medium comprising: code for causing a computer to input a plurality of digital pulses, the digital pulses generated by comparing a received signal to a reference level; code for causing a computer to compute a pulse frequency metric for the digital pulses over a time window; code for causing a computer to accumulate the pulse frequency metric over a plurality of time windows to generate a first accumulated metric; and code for causing a computer to generate a first jammer detection signal if the first accumulated metric exceeds a first threshold.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention can be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. It will be apparent to those skilled in the art that the exemplary embodiments of the invention may be practiced without these specific details. In some instances, well known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary embodiments presented herein.
According to the present disclosure, techniques are provided to detect jammers present in a signal received by a receiver. The techniques described herein may be used for a wireless device, a base station, and other electronics devices. A wireless device may also be referred to as a mobile station, a user equipment, a user terminal, a subscriber unit, etc. A wireless device may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a handheld device, a handset, etc. The techniques may also be used for various communication systems such as Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, etc.
Note the block diagram in
In general, a receiver may be implemented with a super-heterodyne architecture, a direct-to-baseband architecture, or other types of architectures. In the super-heterodyne architecture, the received signal is frequency downconverted in multiple stages, e.g., from RF to an intermediate frequency (IF) in one stage, and then from IF to baseband in another stage. In the direct-to-baseband architecture, the received signal is frequency downconverted from RF directly to baseband in one stage. Different receiver architectures may use different circuit blocks and/or have different requirements. For clarity, the following description is for a direct-to-baseband architecture.
In
Note the block diagram of the jammer detector 200 in
Disclosed further herein are specific exemplary embodiments of the jammer detector blocks described above. Note the exemplary embodiments are given herein for illustrative purposes only, and are not meant to limit the scope of the present disclosure to any particular exemplary embodiments of the jammer detector blocks described. One of ordinary skill in the art will appreciate that the techniques described may be selectively applied to an actual implementation of a jammer detector. For example, the techniques described herein for designing a pulse generator 220 may be combined with techniques for designing a pulse processor 230 other than those described herein. Such exemplary embodiments are contemplated to be within the scope of the present disclosure.
In an exemplary embodiment wherein a transmitter is configured to operate over multiple frequency bands, the notch frequencies of the notch filter 300 may be configured based on the specific frequency band chosen.
In a further exemplary embodiment (not shown), the signal conditioning block 210 may be omitted altogether.
In
The circuitry shown in
As illustrated in
Note the exemplary embodiment depicted in
In an exemplary embodiment (not shown), the circuitry of
In
For example, in an exemplary embodiment wherein the desired RX signal is downconverted to baseband, a close-in jammer may correspond to a low jammer frequency after downconversion, while a far-away jammer may correspond to a higher jammer frequency after downconversion. One of ordinary skill in the art will appreciate that a close-in jammer may then correspond to a low pulse count at the output of the pulse generator output, while a far-away jammer may correspond to a higher pulse count.
At step 610, a number of target pulses Np contained in the output of pulse generator 220 may be counted in a time window indexed by counter i. In an exemplary embodiment, the duration of a time window may correspond to a predetermined number of cycles of a given reference clock, e.g., 512 cycles of a 19.2-MHz XO (crystal oscillator) reference clock. In an exemplary embodiment, the number Np of pulses counted in the time window may be filtered such that they correspond to only those pulses in the output of the pulse generator 220 attributable to jammers that do not originate from TX leakage. Specific exemplary embodiments of the operations carried out in step 610 to achieve such a filtering effect are later described with reference to
At steps 620-640, the number of target pulses Np counted at step 610 are compared to a series of thresholds. In an exemplary embodiment, the thresholds are chosen to determine whether there exist in the pulse generator output: 1) no jammers, 2) close-in jammers, or 3) far-away jammers.
Step 620 determines whether Np falls within a range from 0 to a threshold TNp1, inclusive of 0 and TNp1. If so, counters CCI and CFA may both be decremented by 1 at step 625.
Step 630 determines whether Np falls within a range from TNp1 to a threshold TNp2, inclusive of TNp2. If so, counter CCI may be incremented by 1, while counter CFA may be decremented by 1 at step 635.
Step 640 determines whether Np is greater than TNp2. If so, counter CCI may be decremented by 1, while counter CFA may be incremented by 1 at step 645.
Once Np has been assigned to the appropriate jammer detection range, the method proceeds to step 650. At step 650, the counter CCI is checked to determine whether it exceeds a threshold TCCI, whereupon the method proceeds to issue a CI interrupt at step 655. The execution of step 655 may indicate that a close-in jammer, corresponding to a signal having low frequency after downconversion, has been detected in the pulse generator output. In an exemplary embodiment, the CI interrupt may be a signal originating from digital hardware that is sent to RF RX circuitry, instructing the RF RX circuitry to alter its operation based on the detection of the close-in jammer signals.
At step 660, the counter CFA is checked to determine whether it exceeds a threshold TCFA, whereupon the method proceeds to issue an FA interrupt at step 665. The execution of step 665 may indicate that a far-away jammer, corresponding to a signal having high frequency after downconversion, has been detected in the pulse generator output. In an exemplary embodiment, the thresholds TCCI and TCFA may be equal in value.
At step 670, the counter i is incremented, and the method returns to step 610.
Note the method described with reference to
As earlier mentioned, alternative ways to detect the frequency of target pulses Np over time may also be readily derived by one of ordinary skill in the art. For example, in an alternative exemplary embodiment (not shown), the pulse processor may be configured to measure the time difference between consecutive rising edges in the output signal of the pulse generator. A timer may be programmed to start advancing when a rising edge of the pulse generator output crosses a threshold, and to reset when the next rising edge again crosses the threshold; before the reset, the value of the timer may be used to identify the frequency of the jammer. For example, if the timer value is higher than a first threshold, the pulse processor may declare no jammer detected. If the timer value is lower than the first threshold but higher than a second threshold, the pulse processor may declare a close-in jammer detected. If the timer value is lower than the second threshold, the pulse processor may declare a far-away jammer.
One of ordinary skill in the art will appreciate that while the computation of step 710 may be relatively simple to implement, the number of target pulses Np thus counted may generally include pulses attributable to both TX leakage signals and other jammers. In some cases, it may be undesirable to include pulses attributable to TX leakage signals in the number of target pulses Np. It may be desirable to have an algorithm that includes only pulses not attributable to TX leakage signals in the number of target pulses Np. Such an algorithm may seek to maximize the probability that Np will include pulses due to non-TX leakage signal jammers, while minimizing the probability that Np will include pulses due to the TX-leakage signals.
In
At step 812, the total number of pulses Ns for sub-window s is counted.
At step 814, the method evaluates whether Ns is less than or equal to a threshold Ts. If so, the method proceeds to step 815, wherein Np is incremented by Ns.
At step 816, the parameter s is checked to determine whether the last sub-window in the time window i has been reached. If so, the method continues to the rest of the steps, e.g., step 620 in
One of ordinary skill in the art will realize that the exemplary embodiment shown in
In an exemplary embodiment, the duration of each sub-window and the corresponding threshold Ts may be made dependent on the frequency band of operation. For example, for operation in a 450 MHz RX band, the duration of each sub-window may be 8 cycles of a 19.2-MHz XO reference clock, and Ts may be 1. For operation in a PCS frequency band, the duration of each sub-window may be 2 cycles of the TCXO reference clock, and Ts may be 1. Note the preceding specific values are given for illustration only, and are not meant to limit the scope of the present disclosure to any particular values given.
Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the exemplary embodiments of the invention.
The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Patel, Shrenik, Gudem, Prasad, Palakurty, Saraswathi
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